1. Field of the Invention
This invention is in the field of safety devices for emergency braking devices for railway cars wherein a braking action is automatically applied to the car wheels at the inception of an emergency condition.
2. Description of the Prior Art
Numerous attempts have been made over the years to provide emergency braking of railway cars whenever a car wheel leaves the track or is otherwise in an abnormal separated state from the car frame. The purpose of these devices is to automatically apply an immediate braking force to the car wheels at the inception of an emergency condition. If the emergency condition is sensed sufficiently early, braking is applied to the entire train before all the wheels of the car are derailed, thus minimizing the probability of further derailment and consequent damage. Principal causes of the emergency conditions include broken wheels and truck components, severe slueing or rocking of the car frame, and track obstacles.
In conventional train braking systems, reduction of air pressure in the brake line will cause a braking of the train wheels bringing the train to a stop. In prior art devices, valves have been provided which automatically open or rupture in an emergency condition to relieve the pressure in the brake line to initiate the automatic braking of the train wheels. Examples of the prior art include the devices in the following U.S. Pat. Nos. 624,103; 870,284; 1,205,402; 1,227,913; 1,240,127; 3,938,765 and 3,998,413.
While these devices function in a manner to bring about the desired stopping of the train, they generally do not have complete reliability or are relatively expensive to manufacture. For example, the device in U.S. Pat. No. 1,227,913 is of a construction wherein, due to lack of a rigid mounting of the plug member and due to attachment points of the cable which is connected between the plug member and the wheel truck, the reliability of rupturing the plug member in an emergency condition is impaired.